1. Field of the Disclosure
The present disclosure relates to a method of transmitting broadcast signal, apparatus for processing broadcast signal and method thereof.
2. Discussion of the Related Art
Recently, natural disasters including unexpected earthquakes and floods or emergency situations including terrors, arsons and the like tend to take place more frequently. Natural disasters due to environmental pollution or terrors cause more damages widely and their secondary effects become more powerful. In case that one of the aforesaid emergency takes place, the coverage of the emergency is filed. News relating to the emergency is then broadcasted in a format such as a newsflash and the like on all channels after a prescribed duration.
Basic protocol for processing an emergency alert system message has been determined for televisions and the like for sale in North America. And, a basic protocol for receiving and processing an emergency alert system message correctly is determined for cable digital TVs as well. However, in case that the emergency alert system message defined in the specifications of cable digital TV, e.g., an emergency alert table (hereinafter abbreviated EAT) is intactly applied to a terrestrial broadcasting system, the following problems rise.
First of all, in case of applying an EAT defined for a related art cable digital broadcasting environment to a terrestrial broadcasting system, information on a channel for carrying emergency alert broadcast may be duplicated instead of being unified. For instance, in case of a cable broadcasting system in which a single broadcasting station is capable of managing all channels, channel numbers of all channels broadcasted in-band can be managed using a major channel number (physical channel number) and a minor channel number (program number) only. Yet, in case of terrestrial broadcasting, there exist a plurality of terrestrial broadcasting stations separately. So, a channel number of a channel broadcasted by each of the broadcasting stations can be arbitrarily set. So, the identical major and minor channel numbers may be used by different broadcasting stations.
Secondly, in case of applying the EAT defined in the related art cable digital broadcasting environment to a terrestrial broadcasting system, a relay service provider is able to change a frequency of a channel for carrying emergency alert broadcast arbitrarily in retransmitting the EAT. So, although an emergency takes place, a receiver may be substantially tuned to a channel differing from the initially intended channel for carrying the emergency alert broadcast.